Most oil producing subterranean formations are characterized by pressurized gas. In some parts of the work hydrocarbon bearing formations have pressures sufficient to force liquid hydrocarbons (crude oil) to the earth's surface. In other parts of the world, the gas pressure is not sufficient to force liquid hydrocarbons to the earth's surface. However, in such formations, the presence of gas is nevertheless important since in many formations a gas drive is required to move liquid hydrocarbons from within the formation to the site of a producing well or wells.
As crude oil is extracted from a subterranean reservoir, the reservoir gas pressure decreases. As the gas pressure decreases, crude oil production rates usually fall. For these and other reasons, it has been found desirable in producing many subterranean formations to maintain gas pressure within the formations.
The characteristics of gas injected into a well can be critical. Water or free oxygen contained in gas can cause plugging of formations. Further water or free oxygen can result in bacteria growth that can plug a producing formation.
Ideally, gas injected into a reservoir to augment the production of liquid hydrocarbons should be water-free. Therefore, when treating gas prior to injection, a most important step is to remove substantially all water.
Perhaps even more important than dryness of exhaust gas to be injected into a reservoir to augment the production of hydrocarbons, it is important that the exhaust gas be as free as possible of nitrous oxide, usually referred to in the industry as “NOx”. When nitrous oxide is present in exhaust gas it inevitably comes into contact with water which can be any water vapor that is left within the exhaust gas after efforts are made to improve the dryness of the exhaust gas as much as practically possible, or water that is encountered in subterranean hydrocarbon-producing formations. When nitrous oxide gas encounters water, nitric acid is formed. Nitric acid is exceedingly deleterious to metal and particularly to iron, that is, steel, as used in casing, tubing, pump parts and so forth. Therefore, exhaust gas used to stimulate the production of hydrocarbons should be, to the extent possible, free of NOx.
The present invention provides a process for generating substantially water-free and NOx free exhaust gas that is particularly useful for injection into hydrocarbon bearing formations.
Examples of the use of exhaust gas from an engine for industrial purposes and examples of the use of exhaust gas to augment liquid hydrocarbon production are found in the following United States patents:
Patent NumberInventor(s)Title1,868,755MountDehydrator1,945,407Adair et al.Process of Purifying Gases2,240,550Conlon, Jr.Method of Retuning Gas to Gas-Producing Formations2,825,408WatsonOil Recovery By Subsurface ThermalProcessing3,000,707BarstowProcess For Generating Inert Gas3,004,601BodineMethod and Apparatus for Augmenting OilRecovery from Wells by Refrigeration3,100,528Plummer, et al.Method for Using Inert Gas3,137,344WiemerMinimizing Loss of Driving Fluids in SecondaryRecovery3,381,523NettlesMethod and Apparatus for Supplying Gas UnderPressure3,653,438WagnerMethod of Recovery of Petroleum Deposits3,908,762RedfordMethod for Establishing Communication Path inviscous Petroleum-Containing FormationsIncluding Tar Sand Deposits for Use in OilRecovery Operations4,324,291Wong et al.Viscous Oil Recovery Method4,325,432HenryMethod of Oil Recovery4,533,374HaagMethod for Reducing Air Pollution4,546,829Martin et al.Enhanced Oil Recovery Process4,593,763BurkeCarbon Dioxide Well Injection Method4,891,939BrighentiSystem for the Cryogenic Processing andStorage of Combustion Products of HeatEngines5,232,049Christiansen, etSequentially flooding a Subterraneanal.Hydrocarbon-Bearing Formation with aRepeating Cycle of Immiscible DisplacementGases5,953,907Kato et al.Method of Controlling An Engine Exhaust GasSystem and Method of Detecting DeteriorationOf Catalyst/Absorbing Means5,988,280Crawford et al.Use of Engine Heat in Treating a Well Bore6,039,116Stevenson et al.Oil and Gas Production with Periodic GasInjection